The last number of the London _Quarterly Review_ presents a new candidate for the honor of the authorship of JUNIUS, in the person of the second Lord LYTTLETON--best known in his lifetime for profligacy, and since, for the curious circumstances attending his death, which are well related in Sir Walter Scott's _Demonology and Witchcraft_. The reviewer proves Lord Lyttleton capable of writing the letters; that he had motives to write them; that his conduct on other occasions is consistent with Junius's anxiety to preserve his incognito; and that there are curious coincidences between his character and conduct, and many characteristic passages in the letters. This directs research to a new quarter; but though a good _prima facie_ case of suspicion is made out, that is all. Positive evidence is wanted. A writer in the London _Athenaeum_, who long ago demolished the claims of Sir Philip Francis to be considered Junius (Lord Mahon's judgment to the contrary notwithstanding), and who has since pretty satisfactorily disposed of the dozen or more other prominent claimants, has, we think, conclusively answered the _Quarterly's_ claim in behalf of Lord Lyttleton. We should like to know who the critic of the _Athenaeum_ supposes to be the Great Unknown. In one of the volumes of the _Grenville Papers_, just published in London, the author says: "With respect to the letters addressed to Mr. Grenville by the author of 'Junius,' which will be printed in the concluding volumes of this correspondence, it will be sufficient to say for the present, that there is not a particle of truth in all the absurd tales that have been invented, as to their preservation or discovery. In the proper place I shall have an opportunity of explaining that there was no mystery attaching to them, beyond the anonymous nature of the author's communication." This is rather unfavorable, as far as it goes, to the hypothesis of Lyttelton's having been the author. It throws us back upon Sir David Brewster's claim in behalf of Mr. Maclean. Upon that theory, probably, the archives of London House could throw some light. It may be mentioned, with reference to this subject that the _Grenville Papers_ go far to substantiate Lord Shelburne's title to the designation of _Malagrida_. * * * * * We find in the _Athenaeum_ an account of a curious case, having considerable interest for the lovers of old Italian literature, which has just been decided by the Sacred Council in Rome.